Abstract: A traumatic brain injury diagnostic system may comprise a current transmission unit, a voltage detection unit, a demodulation unit, and at least one processor. The current transmission unit may output an electric current to at least a first pair of electrodes attached to a head of a subject. The voltage detection unit may detect a voltage via at least a second pair of electrodes attached to the head of the subject proximal to the first pair of electrodes. The demodulation unit may extract an electrical impedance signal from an output electric current of the current transmission unit and the detected voltage of the voltage detection unit. The processor may perform operations to diagnose traumatic brain injury including comparing a static component of the electrical impedance signal to a pre-defined threshold and comparing a dynamic component of the electrical impedance signal to a pre-defined dynamic value.